1. Field of the Invention
The present invention relates to a liquid forced-feed apparatus for feeding a liquid such as water, fuel, etc. under pressure. The liquid forced-feed apparatus of the present invention is suitable particularly for use in collecting a condensate generated in a steam piping system and feeding this condensate to a boiler or a waste heat recovery system, to thereby act as a trap or pump-trap combination.
2. Description of the Prior Art
Condensate generated in a steam piping system in most cases still has a considerable quantity of stored waste heat. Therefore it has been a widespread practice to use a condensate recovery system including a liquid forced-feed apparatus, in the form of a trap, for recovering the condensate and feeding it into a boiler or a waste heat recovery system. Such a system is for the purpose of utilization of waste heat from the condensate, thus realizing the effective use of this energy.
The liquid forced-feed apparatus used in condensate recovery systems collects condensate in a hermetic vessel, and introduces a high-pressure working fluid such as steam into the hermetic vessel by operating a change-over valve, thereby discharging the condensate from the inside of the hermetic vessel under the pressure of the working fluid.
To insure high-efficiency operation of the liquid forced-feed apparatus, it is necessary to collect as much condensate as possible within the hermetic vessel and to properly switch the change-over valve. The liquid forced-feed apparatus of the prior art, therefore, generally use a snap mechanism provided with a coil spring, in order to insure reliable switching of the change-over valve. One prior art liquid forced-feed apparatus which is equipped with a built-in snap mechanism using a coil spring is disclosed in U.S. Pat. No. 5,141,405.
FIG. 1 is a front view of a snap mechanism used in the prior art liquid forced-feed apparatus of U.S. Pat. No. 5,141,405. In the liquid forced-feed apparatus disclosed in the U.S. Pat. No. 5,141,405 the snap mechanism 100 includes a float arm 101, a sub-arm 102, and a coil spring 103 in a compressed condition. The main arm 101 is rotatably supported on a pin 106 in relation to a supporting member 105. On the forward end of the float arm 101 is connected a float 108.
The sub-arm 102 is connected at one end to the supporting member 105 by the same pin 106 as the float arm 101, and at the other end to one end of the coil spring 103 by a pin 110 through a spring bracket member 116. On the central part of the sub-arm 102 is connected a valve spindle operating rod 111, by a pin 107. The valve spindle operating rod 111 is connected to a change-over valve (not shown), and the snapping mechanism 100 is linked to the change-over valve through the valve spindle operating rod 111.
The other end of the coil spring 103 in FIG. 1 is connected to the float arm 101 by a pin 112, through a spring bracket member 115. In the prior art liquid forced-feed apparatus of U.S. Pat. No. 5,141,405 shown in FIG. 1, with the accumulation of condensate in the hermetic vessel (not shown), the float 108 rises. As the float 108 rises, the spring bracket member 115 side of the coil spring 103 moves upward with the rise of the float 108, thus compressing to deform the coil spring 103. Rising of the float 108 causes the coil spring 103 to move in line with the sub-arm 102, and with further rising of the float 108--until an angle between the coil spring 103 and the sub-arm 102 exceeds 180 degrees--the coil spring 103 suddenly recovers from deformation, and the connecting section (the pin 110) between the coil spring 103 and the sub-arm 102 snaps downward, resulting in downward movement of the valve spindle operating rod 111 connected to the sub-arm 102 to thereby switch the change-over valve (not shown).